1. Heat cream, butter and espresso powder in a heavy saucepan stirring often. Turn off the heat just before it begins to boil and stir with a whisk.
2. Pour heated mixture over chopped chocolate and let sit for a minute. Then whisk together until the chocolate and cream are combined, melted and smooth.

3. Pour the chocolate ganache in a small baking pan. Cool to room temperature and then place in the refrigerator to chill for about 30 minutes. Use a small scoop to form round balls of ganache and place on a wax paper covered baking sheet. Reshape by hand if needed and return to refrigerator to chill for several minutes.
4. Roll balls in cocoa powder to coat.
5. Keep refrigerated until serving.